Summary: | Do Sun Kwon,1,* Yong Jun Choi,2,* Tae Hee Kim,2 Min Kwang Byun,2 Jae Hwa Cho,2 Hyung Jung Kim,2 Hye Jung Park2 1Department of Internal Medicine, Hallym Hospital, Incheon, Korea; 2Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea*These authors contributed equally to this workCorrespondence: Hye Jung Park Department of Internal MedicineGangnam Severance Hospital, Yonsei University College of Medicine, 211 Eonju-Ro, Gangnam-Gu, Seoul 60273, Republic of KoreaTel +82-2-2019-3302Fax +82-2-3463-3882Email craft7820@yuhs.acPurpose: The forced mid-expiratory flow (FEF25-75%) value is a potentially sensitive marker of obstructive peripheral airflow. We aimed to assess whether FEF25-75% can be an early predictor of chronic obstructive pulmonary disease (COPD).Patients and Methods: Between July 1, 2007 and June 31, 2009, we identified 3624 patients who underwent a pulmonary function test (PFT) in Gangnam Severance Hospital. We selected 307 patients aged over 40 years without COPD who had normal PFT results at baseline and who had follow-up PFT records more than 1 year later. A FEF25-75% z-score less than − 0.8435 was considered low. We defined COPD as a forced expiratory volume in one second/forced vital capacity value of less than 0.7 before July 31, 2019.Results: Among 307 patients, 91 (29.6%) had low FEF25-75% at baseline. After 10 years, the incidence rate of COPD in the low FEF25-75% group was significantly higher than that in the normal FEF25-75% group (41.8% vs 7.4%; P-value< 0.001). The Cox proportional hazard model showed that age (hazard ratio [HR] 1.09; P-value< 0.001), smoking status (occasional smoker HR, 4.59; P-value< 0.001 and long-term smoker HR, 2.18; P-value=0.023), and low FEF25-75% (HR, 3.31; P-value< 0.001) were predictive factors for the development of COPD.Conclusion: The FEF25-75% value in patients with normal lung function is a useful predictor for the development of COPD. We should carefully monitor patients who present with low FEF25-75% values, even if they have normal lung function.Keywords: COPD, respiratory function tests, tobacco
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